Connector for measuring electric resistance, apparatus and method for measuring electric resistance of circuit board

ABSTRACT

A connector for measurement of electric resistance, an electric resistance-measuring apparatus for circuit boards, and methods of measurement of electric resistance. The connector includes an insulating base plate, a plurality of connecting electrode pairs provided on a front surface of the insulating base plate, and composed of core electrodes arranged in accordance with a pattern corresponding to a pattern of a plurality of electrodes to be inspected in a circuit board to be inspected and ring-like electrodes arranged to surround the respective core electrodes in a state electrically insulated from the core electrodes, and a plurality of relay electrodes provided on a back surface of the insulating base plate and electrically connected to either one of the core electrode or ring-like electrode of the connecting electrode pairs.

TECHNICAL FIELD

The present invention relates to a connector for measurement of electricresistance, and electric resistance-measuring apparatus for circuitboard and method of measurement.

BACKGROUND ART

In recent years, with the request for speeding-up of signal transmissionin electronic parts and electronic equipments containing such a parttherein, there has been a demand for development of those low inelectric resistance of wiring between electrodes as circuit boards forfabricating LSI packages such as BGA and CSP or circuit boards, on whichthese semiconductor devices are mounted. Therefore, it is extremelyimportant to measure the electric resistance of wiring betweenelectrodes of such a circuit board with high precision in electricalinspection of the circuit board.

In the measurement of an electric resistance of a circuit board, therehas heretofore been adopted, for example, the four probe method, inwhich probes PA and PD for current supply and probes PB and PC forvoltage measurement are pressed against and brought into contact withrespective 2 electrodes 91 and 92 to be inspected, which have beenelectrically connected to each other in a circuit board 90 to beinspected, as illustrated in FIG. 11, a current is supplied between theprobes PA and PD for current supply from a power supply device 93 inthis state, and a voltage signal detected by the probes PB and PC forvoltage measurement at this time is processed in an electric signalprocessor 94, thereby finding an electric resistance value between theelectrodes 91 and 92 to be inspected.

In the method described above, however, the surfaces of the electrodes91 and 92 to be inspected may be damaged by pressing the probes becauseit is necessary to bring the probes PA and PD for current supply and theprobes PB and PC for voltage measurement into contact with therespective electrodes 91 and 92 to be inspected by considerably highpressing force, the probes are made of a metal, and the tips thereof arepointed. Therefore the circuit board becomes impossible to be used.Under such circumstances, the electric resistance measurement cannot beperformed on all circuit boards to be provided as products, and soso-called sampling inspection has to be performed. After all, the yieldof the products cannot be increased.

In order to solve such a problem, there have heretofore been proposedelectric resistance-measuring apparatus, in which a connecting membercoming into contact with electrodes to be inspected is formed by aconductive elastomer.

For example, (i) Japanese Patent Application Laid-Open No. 26446/1997discloses an electric resistance-measuring apparatus, in which elasticconnecting members formed of conductive rubber obtained by bindingconductive particles with an elastomer are arranged at electrodes forcurrent supply and electrodes for voltage measurement, respectively,(ii) Japanese Patent Application Laid-Open No. 2000-74965 discloses anelectric resistance-measuring apparatus having a common elasticconnecting member formed of an anisotropically conductive elastomer,which is provided so as to come into contact with surfaces of bothelectrode for current supply and electrode for voltage measurementelectrically connected to the same electrode to be inspected, and (iii)Japanese Patent Application Laid-Open No. 2000-241485 discloses anelectric resistance-measuring apparatus comprising a circuit board forinspection, on the surface of which a plurality of inspection electrodeshave been formed, and an elastic connecting member formed of aconductive elastomer, which is and provided on the surface of thecircuit board for inspection, wherein 2 electrodes of the inspectionelectrodes are selected in a state that electrodes to be inspected havebeen electrically connected to the plurality of the inspectionelectrodes through the connecting member, one of both electrodes is usedas an electrode for current supply, and the other is used as anelectrode for voltage measurement to measure an electric resistance.

According to such electric resistance-measuring apparatus, an electrodefor current supply and an electrode for voltage measurement are broughtinto contact with electrodes to be inspected of a circuit board to beinspected through the elastic connecting member, whereby electricalconnection is achieved, so that the measurement of the electricresistance can be conducted without damaging the electrodes to beinspected.

However, the measurement of an electric resistance between electrodes bythe electric resistance-measuring apparatus of the construction (i) or(ii) involves the following problems.

In recent years, the size and pitch or interelectrode distance ofelectrodes in a circuit board have tended to become small for thepurpose of achieving a high degree of integration. In the electricresistance-measuring apparatus of the construction (i) or (ii), however,it is necessary to electrically connect both electrodes for currentsupply and electrodes for voltage measurement at the same time toelectrodes to be inspected in a circuit board to be inspected, which issubjected to electric resistance measurement, through the elasticconnecting member, respectively. In the electric resistance-measurementapparatus for measuring an electric resistance as to a circuit board tobe inspected, on which small-sized electrodes to be inspected have beenarranged at a high density, accordingly, it is thus necessary to formelectrodes for current supply and electrodes for voltage measurement ina state separated from one another, corresponding to individualsmall-sized electrodes to be inspected, in a region of an area equal toor smaller than a region occupied by the electrodes to be inspected,i.e., to form electrodes for current supply and electrodes for voltagemeasurement smaller in size than the electrodes to be inspected in astate separated from one another at an extremely short distance.

On the other hand, in order to improve productivity, a productionprocess to produce a plurality of circuit board separated from eachother by producing a combined circuit board composed of a plurality ofcircuit boards linked together from a base plate material, collectivelyconducting electrical inspection as to the respective circuit boards inthe combined circuit board in this state and then cutting the combinedcircuit board is adapted.

However, since the area of the combined circuit board, which is aninspection target, is considerably large, and number of electrodes to beinspected is also extremely great, and, when multi-layer circuit boardsare produced in particular, the number of steps in the productionprocess thereof is great, and the number of times subjected to thermalhysteresis history by a heating treatment is great, the electrodes to beinspected are often formed in a state misregistered from the prescribedarrangement positions. When measurement of an electric resistance isperformed as to the circuit boards to be inspected, which are large inarea and have a great number of electrodes to be inspected formed in astate misregistered from the prescribed arrangement positions, by theelectric resistance-measuring apparatus of the construction (i) or (ii),it is extremely difficult to electrically connect both electrodes forcurrent supply and electrodes for voltage measurement at the same timeto the respective electrodes to be inspected.

Description is given by a specific example. When an electric resistanceas to an electrode T to be inspected having a diameter L of 300 μm asshown in FIG. 12 is measured, a clearance D between an electrode A forcurrent supply and an electrode V for voltage measurement to beelectrically connected to the electrode T to be inspected is about 150μm. When the position of the electrode T to be inspected to theelectrode A for current supply and the electrode V for voltagemeasurement deviates from the prescribed position shown in FIG. 12 by 75μm in a direction that the electrode A for current supply and theelectrode V for voltage measurement are arranged in alignment of acircuit board to be inspected as shown in FIGS. 13( a) and 13(b),electrical connection between either one of the electrode A for currentsupply or the electrode V for voltage measurement and the electrode T tobe inspected is not achieved, and so necessary measurement of theelectric resistance cannot be conducted.

As a means for solving such a problem, it is considered to make theclearance D between the electrode A for current supply and the electrodeV for voltage measurement smaller, for example, to an extent of 100 μmor smaller. It is however extremely difficult in fact to produce such anelectric resistance-measuring apparatus.

On the other hand, according to the electric resistance-measuringapparatus (iii), there is no need to form electrodes for current supplyand electrodes for voltage measurement corresponding to individualelectrodes to be inspected, and so capacity for misregistration toelectrodes to be inspected becomes high even when a circuit board to beinspected which is subjected to the measurement of electric resistanceis large in area and has a great number of electrodes to be inspected,and the small-sized electrodes to be inspected are arranged at a highdensity. In addition, such an electric resistance-measuring apparatus iseasily produced.

However, such an electric resistance-measuring apparatus is great inmeasurement error range because it is a measuring apparatus according tothe so-called pseudo-four-probe method, and so it is difficult toperform electric resistance measurement as to a circuit board low inelectric resistance between electrodes with high precision.

DISCLOSURE OF THE INVENTION

The present invention has been made on the basis of the foregoingcircumstances and has as its first object the provision of a connectorfor measurement of electric resistance, and an electricresistance-measuring apparatus for circuit boards and method ofmeasurement of electric resistance, by which necessary electricalconnection to a circuit board to be inspected, which is subjected toelectric resistance measurement, can be surely achieved even when thecircuit board to be inspected is large in area and has a great number ofsmall-sized electrodes to be inspected, and expected measurement ofelectric resistance can be surely performed with high precision.

According to the present invention, there is provided a connector formeasurement of electric resistance, comprising

an insulating base plate,

a plurality of connecting electrode pairs provided on a front surface ofthe insulating base plate and, composed of core electrodes arranged inaccordance with a pattern corresponding to a pattern of a plurality ofelectrodes to be inspected in a circuit board to be inspected, which issubjected to electric resistance measurement and ring-like electrodesarranged so as to surround the respective core electrodes in a stateelectrically insulated from the core electrodes, and

a plurality of relay electrodes provided on a back surface of theinsulating base plate and electrically connected to either one of thecore electrode or ring-like electrode in the connecting electrode pairs.

According to the present invention, there is provided an electricresistance-measuring apparatus for circuit boards, comprising theabove-described connector for measurement of electric resistancearranged on one side of a circuit board to be inspected, which issubjected to electric resistance measurement, wherein

the core electrodes and ring-like electrodes of the connecting electrodepairs of the connector for measurement of electric resistance areelectrically connected at the same time to respective one-sideelectrodes to be inspected in the circuit board to be inspected, therebyrealizing a measurable state, and

in this measurable state, one of the core electrode and ring-likeelectrode electrically connected to one designated one-side electrode tobe inspected is used as an electrode for current supply, and the otheris used as an electrode for voltage measurement, thereby performingmeasurement of electric resistance related to the designated oneone-side electrode to be inspected.

The electric resistance-measuring apparatus for circuit boards accordingto the present invention may preferably comprise a one-side circuitboard for inspection arranged on a back surface of the connector formeasurement of electric resistance through an anisotropically conductivesheet and having, on its surface, inspection electrodes arranged inaccordance with a pattern corresponding to a pattern of the relayelectrodes of the connector for measurement of electric resistance,wherein

in the measurable state, the inspection electrodes are electricallyconnected with their corresponding relay electrodes through theanisotropically conductive sheet.

The electric resistance-measuring apparatus for circuit boards maypreferably further comprise an other-side circuit board for inspectionarranged on the other side of the circuit board to be inspected, wherein

the other-side circuit board for inspection has, on its surface,inspection electrodes for current supply and inspection electrodes forvoltage measurement, which are arranged in a state separated from eachother corresponding to other-side electrodes to be inspected of thecircuit board to be inspected and electrically connected to the sameother-side electrodes to be inspected.

According to the present invention, there is provided a method ofmeasurement of electric resistance for circuit boards, which comprisesarranging the above-described connector for measurement of electricresistance on one side of a circuit board to be inspected, which issubjected to electric resistance measurement,

electrically connecting the core electrodes and ring-like electrodes ofthe connecting electrode pairs of the connector for measurement ofelectric resistance at the same time to respective one-side electrodesto be inspected of the circuit board to be inspected, thereby realizinga measurable state, and

in this measurable state, using one of the core electrode and ring-likeelectrode electrically connected to one designated one-side electrode tobe inspected as an electrode for current supply and the other as anelectrode for voltage measurement, thereby performing measurement ofelectric resistance related to the designated a one-side electrode to beinspected.

According to the connector for measurement of electric resistance of theabove-described construction, the connector has core electrodes arrangedin accordance with a pattern corresponding to a pattern of electrodes tobe inspected in a circuit board to be inspected and ring-like electrodesarranged so as to surround the respective core electrodes, so that atleast a part of the ring-like electrode is located on the electrode tobe inspected in the circuit board to be inspected so far as alignment isconducted in such a manner that at least a part of the core electrode islocated on the electrode to be inspected, whereby electrical connectionof both core electrodes and ring-like electrodes to the electrodes to beinspected is surely achieved.

In addition, since the core electrodes and ring-like electrodes areelectrically insulated from each other, an electric resistance as to thecircuit board to be inspected can be measured with high precision byusing one of the core electrode and ring-like electrode electricallyconnected to the electrode to be inspected as an electrode for currentsupply and the other as an electrode for voltage measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating the construction of anexemplary connector for measurement of electric resistance according tothe present invention.

FIG. 2 illustrates electrode arrangement on a front surface of theconnector for measurement of electric resistance shown in FIG. 1.

FIG. 3 illustrates electrode arrangement on a back surface of theconnector for measurement of electric resistance shown in FIG. 1.

FIG. 4 is a cross-sectional view illustrating a state that the connectorfor measurement of electric resistance shown in FIG. 1 has been arrangedon one surface of a circuit board to be inspected.

FIG. 5 illustrates a state that misregistration has occurred betweenelectrodes to be inspected and connecting electrode pairs.

FIG. 6 is a sectional view illustrating the construction of a circuitboard to be inspected.

FIG. 7 is a cross-sectional view illustrating a principal part of aconnector for measurement of electric resistance according to anotherembodiment of the present invention.

FIG. 8 is a cross-sectional view schematically illustrating theconstruction of an electric resistance-measuring apparatus for circuitboards according to an embodiment of the present invention together witha circuit board to be inspected.

FIG. 9 is a cross-sectional view, on an enlarged scale, illustrating aprincipal part of the electric resistance-measuring apparatus forcircuit boards shown in FIG. 8.

FIG. 10 is a cross-sectional view illustrating the construction of aprincipal part of an electric resistance-measuring apparatus for circuitboards according to another embodiment of the present invention togetherwith a circuit board to be inspected.

FIG. 11 typically illustrates an apparatus for measuring an electricresistance between electrodes in a circuit board by probes for currentsupply and probes for voltage measurement.

FIG. 12 illustrates a state that an electrode for current supply and anelectrode for voltage measurement have been correctly arranged on anelectrode to be inspected in a conventional electricresistance-measuring apparatus for circuit boards.

FIG. 13 illustrates a state that an electrode for current supply and anelectrode for voltage measurement have been arranged in a statemisregistered on an electrode to be inspected in a conventional electricresistance-measuring apparatus for circuit boards.

DESCRIPTION OF CHARACTERS

-   -   1 Circuit board to be inspected,    -   2 One-side electrodes to be inspected,    -   3 Other-side electrodes to be inspected,    -   5 Anisotropically conductive sheet,    -   10 Connector for measurement of electric resistance,    -   11 Insulating base plate, 12 Conductors    -   13 Core electrodes, 14 Relay electrodes,    -   15 Ring-like electrodes,    -   16 Connecting electrode pairs,    -   17 Relay electrodes, 18 Wiring part,    -   19 Short circuit parts,    -   20 First upper-side anisotropically conductive sheet,    -   21 Conductive path-forming parts,    -   22 Insulating parts,    -   25 Third upper-side anisotropically conductive sheet,    -   40 Upper-side adaptor,    -   41 One-side circuit board for inspection,    -   42 Inspection electrodes, 43 Terminal electrodes,    -   47 Second upper-side anisotropically conductive sheet,    -   48 Electrode plate,    -   49 Standard arrangement electrodes,    -   50 Lower-side adaptor,    -   51 Other-side circuit board for inspection,    -   52 Inspection electrodes for current supply,    -   52 a Terminal electrodes for current supply,    -   53 Inspection electrodes for voltage measurement,    -   53 a Terminal electrodes for voltage measurement,    -   56 Elastic connecting member,    -   57 Holding member, 59 Tester,    -   60 Electrode plate,    -   61 Standard arrangement electrodes,    -   62 Lower-side anisotropically conductive sheet,    -   90 Circuit board to be inspected,    -   91, 92 Electrodes to be inspected,    -   93 Power supply device,    -   94 Electric signal processor,    -   PA, PD Probes for current supply,    -   PB, PC Probes for voltage measurement,    -   A Electrode for current supply,    -   V Electrode for voltage measurement,    -   T Electrode to be inspected,    -   P Conductive particles

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will hereinafter be describedin details.

<Connector for Measurement of Electric Resistance>

FIG. 1 is a cross-sectional view illustrating the construction of a partof an exemplary connector for measurement of electric resistanceaccording to the present invention. This connector 10 for measurement ofelectric resistance is used for measuring an electric resistance betweenelectrodes in a circuit board.

The connector for measurement of electric resistance shown in FIG. 1 hasan insulating base plate 11. In the insulating base plate 11, aplurality of truncated cone-like conductors 12, which become graduallygreater in diameter as they go toward a back surface from a frontsurface thereof, are formed in accordance with a pattern correspondingto a pattern of electrodes to be inspected in a circuit board, which issubjected to electric resistance measurement, so as to extend through ina thickness-wise direction of the insulating base plate and project fromboth surfaces thereof. A core electrode 13 is formed by an end part onthe front surface side of each of the conductors 12, and a relayelectrode 14 is formed by the other end part on the back surface side ofthe conductor 12.

As illustrated in FIG. 2 also, a plurality of ring-like electrodes 15surrounding the respective core electrodes 13 are arranged on the frontsurface (lower surface in FIG. 1) of the insulating base plate 11 so asto project from the front surface of the insulating base plate 11 in astate electrically insulated from the core electrodes 13. A connectingelectrode pair 16 to be electrically connected to an electrode to beinspected in a circuit board to be inspected is formed by each of thecore electrodes 13 and the ring-like electrode 15 surrounding it. In theembodiment illustrated, the projected heights from the surface of theinsulating base plate 11 of the core electrodes 13 and the ring-likeelectrodes 15 are substantially the same as each other.

As illustrated in FIG. 3 also, a plurality of relay electrodes 17independent from the relay electrodes 14 by the conductors 12 are formedat positions between the relay electrodes 14 by the adjacent conductors12 on the back surface (upper surface in FIG. 1) of the insulating baseplate 11. The each of relay electrodes 17 are electrically connected totheir corresponding ring-like electrodes 15 through a wiring part 18formed on the front surface of the insulating base plate 11 and shortcircuit parts 19 extending through in the thickness-wise direction ofthe insulating base plate 11.

As a material for forming the insulating base plate 11, may be used apolyimide resin, glass fiber-reinforced polyimide resin, glassfiber-reinforced epoxy resin, glass fiber-reinforced bismaleimidetriazine resin or the like. The insulating base plate 11 may be asingly-layer structure or multi-layer structure.

The thickness of the insulating base plate 11 is preferably, forexample, 50 to 1,000 μm, more preferably 100 to 500 μm.

As a material for forming the core electrodes 13, i.e., the conductors12, may be used a metal such as nickel, iron, cobalt, copper, gold,silver or aluminum, an alloy thereof, a laminate thereof, or a curedproduct of a conductive paste containing powder of these metals.However, a metal is preferably used in that high conductivity isachieved.

The diameter of the core electrodes 13 is preset according to thediameter of electrodes to be inspected electrically connected to therespective core electrodes 13 and is preferably 30 to 80%, morepreferably 40 to 60% of the diameter of the electrodes to be inspectedin that electrical connection to the electrodes to be inspected can besurely achieved.

The projected height of the core electrodes 13 from the insulating baseplate 11 is preferably 20 to 100 μm, more preferably 30 to 70 μm.

As a material for forming the ring-like electrodes 15, may be usedcopper, nickel, gold or a laminate of these metals.

The inner diameter of the ring-like electrodes 15 is preset according tothe diameter of electrodes to be inspected electrically connected to therespective ring-like electrodes 15 and is preferably 50 to 110%, morepreferably 70 to 100%, particularly preferably 75 to 95% of the diameterof the electrodes to be inspected in that electrical connection to theelectrodes to be inspected can be surely achieved.

The inner diameter of the ring-like electrodes 15 is preferably 1.1 to 2times, more preferably 1.2 to 1.7 times of the diameter of the coreelectrodes 13 from the viewpoint of surely retaining the insulatingproperties between the core electrodes 13 and the ring-like electrodes15.

The projected height of the ring-like electrodes 15 from the insulatingbase plate 11 is preferably 20 to 100 μm, more preferably 30 to 70 μm.

The conductors 12 can be formed by, for example, forming through-holesin the insulating base plate 11 by a proper meaning, for example,drilling or laser beam machining, and filling in the through-holes witha metal by a plating treatment or the like or filling in them with aconductive paste to subject the conductive paste to a curing treatment.

The ring-like electrodes 15, relay electrodes 17, wiring parts 18 andshort circuit parts 19 can be formed by a method generally used forproducing a printed wiring board.

The connector 10 for measurement of electric resistance is arranged onone surface of a circuit board 1 to be inspected, which is subjected toelectric resistance measurement, through, for example, ananisotropically conductive sheet 5 in such a manner that respective coreelectrodes 13 in the connector 10 for measurement of electric resistanceare located on the respective one-side electrodes 2 to be inspected of acircuit board 1 to be inspected as illustrated in FIG. 4, and pressed bya proper meaning, thereby, the connecting electrode pairs 16 of theconnector 10 for measurement of electric resistance are electricallyconnected to the one-side electrodes 2 to be inspected of the circuitboard 1 to be inspected through an anisotropically conductive sheet 5.

At this time, even when the central positions of the core electrodes 13deviate from the respective central positions of the one-side electrodes2 to be inspected as illustrated in FIG. 5, the ring-like electrodes 15are certainly electrically connected to the one-side electrodes 2 to beinspected so far as the core electrodes 13 are electrically connected tothe respective one-side electrodes 2 to be inspected because thering-like electrodes 15 are formed so as to surround the respective coreelectrodes 13.

In such a state, one of a plurality of the one-side electrodes 2 to beinspected in the circuit board 1 to be inspected is designated, and oneof the core electrode 13 and ring-like electrode 15 electricallyconnected to this designated electrode 2 to be inspected is used as anelectrode for current supply, and the other is used as an electrode forvoltage measurement, thereby performing measurement of an electricresistance related to the designated one-side electrode 2 to beinspected.

The circuit board 1 to be inspected, which is subjected to electricresistance measurement, may be any of a circuit board having onlyone-side electrodes 2 to be inspected formed on one surface thereof andhaving only a circuit 4 a formed between the one-side electrodes 2 to beinspected as illustrated in FIG. 6( a), a circuit board having one-sideelectrodes 2 to be inspected formed on one surface thereof andother-side electrodes 3 to be inspected formed on the other side andhaving only a circuit 4 b formed between the one-side electrode 2 to beinspected and the other-side electrode 3 to be inspected as illustratedin FIG. 6( b), and a circuit board having one-side electrodes 2 to beinspected formed on one surface thereof and the other-side electrodes 3to be inspected formed on the other side and having both circuit 4 aformed between the one-side electrodes 2 to be inspected and circuit 4 bformed between the one-side electrode 2 to be inspected and theother-side electrode 3 to be inspected as illustrated in FIG. 6( c).

According to the connector 10 for measurement of electric resistance ofthe above-described construction, the ring-like electrodes 15 are formedabout the respective core electrodes 13 arranged in accordance with apattern corresponding to a pattern of the one-side electrodes 2 to beinspected in the circuit board 1 to be inspected so as to surround therespective core electrodes 13, so that at least a part of the ring-likeelectrode 15 is located on the one-side electrode 2 to be inspected inthe circuit board 1 to be inspected so far as alignment is conducted insuch a manner that at least a part of the core electrode 13 is locatedon the one-side electrode 2 to be inspected. Accordingly, electricalconnection of both core electrodes 13 and ring-like electrodes 15 to theone-side electrodes 2 to be inspected can be surely achieved even whenthe circuit board 1 to be inspected is large in area and has a greatnumber of small-sized one-side electrodes 2 to be inspected. Inaddition, since the core electrodes 13 and ring-like electrodes 15 areelectrically insulated from each other, an electric resistance as to thecircuit board 1 to be inspected can be measured with high precision byusing one of the core electrode 13 and ring-like electrode 15electrically connected to the one-side electrode 2 to be inspected as anelectrode for current supply and the other as an electrode for voltagemeasurement.

In the connector for measurement of electric resistance according to thepresent invention, various changes or modifications may be added withoutbeing limited to the above-described embodiment.

For example, the conductors 12 may have a structure that they aresupported movably in a thickness-wise direction of the insulating baseplate 11 as illustrated in FIG. 7, specifically, a structure thattapered through-holes, which extend through in the thickness-wisedirection and become gradually greater in diameter as they go toward aback surface from a front surface of the base plate 11, are formed inthe insulating base plate 11, and each of truncated cone-like conductors12 fitted to the respective through-holes is supported movably in thethickness-wise direction so as to separate from and contact with theinner wall surface of the through-hole.

According to such a structure, the core electrode 13, i.e., theconductor 12 is moved in the thickness-wise direction according to theprojected height of the electrode to be inspected, so that theirregularity-absorbing property of the anisotropically conductive sheetarranged on the front surface of the connector 10 for measurement ofelectric resistance can be effectively utilized, whereby highreliability on connection is achieved even to a circuit board to beinspected that has, for example, protruding electrodes to be inspected,a scatter of projected height of said protruding electrodes to beinspected being great. As a result, necessary measurement of electricresistance can be surely performed with high precision.

<Electric Resistance-Measuring Apparatus for Circuit Board>

FIG. 8 illustrates the construction of an electric resistance-measuringapparatus for circuit boards according to an embodiment of the presentinvention, and FIG. 9 is a cross-sectional view, on an enlarged scale,illustrating a principal part of the electric resistance-measuringapparatus for circuit boards shown in FIG. 8.

This electric resistance-measuring apparatus for circuit boards isconstructed by vertically arranging an upper-side adaptor 40 arranged onone side (upper surface side in FIG. 8) of a circuit board 1 to beinspected, the electric resistance of which should be measured, and alower-side adaptor 50 arranged on the other side (lower surface side inFIG. 8) of the circuit board 1 to be inspected in opposed relation toeach other.

In the upper-side adaptor 40, a connector 10 for measurement of electricresistance of the construction shown in, for example, FIG. 1, which isarranged on one side (upper side in FIG. 8) of the circuit board 1 to beinspected, is provided. On the back surface (upper surface in FIG. 8) ofthe connector 10 for measurement of electric resistance, a one-sidecircuit board 41 for inspection is arranged through a first upper-sideanisotropically conductive sheet 20. A plurality of inspectionelectrodes 42 are arranged on a front surface (lower surface in FIG. 8)of this one-side circuit board 41 for inspection according to a patterncorresponding to a pattern of the relay electrodes 14, 17 in theconnector 10 for measurement of electric resistance. On the back surface(upper surface in FIG. 8) of the one-side circuit board 41 forinspection, terminal electrodes 43 are arranged in accordance with apattern corresponding to an arrangement pattern of standard arrangementelectrodes 49 of an electrode plate 48, which will be describedsubsequently, and the respective terminal electrodes 43 are electricallyconnected to their corresponding inspection electrodes 42.

An electrode plate 48 is provided on the back surface of the one-sidecircuit board 41 for inspection through a second upper-sideanisotropically conductive sheet 47. This electrode plate 48 has, on thefront surface (lower surface in FIG. 8) thereof, standard arrangementelectrodes 49 arranged on standard lattice points having a pitch of, forexample, 2.54 mm, 1.8 mm or 1.27 mm. The standard arrangement electrodes49 are respectively electrically connected to the terminal electrodes 43of the one-side circuit board 41 for inspection through the secondupper-side anisotropically conductive sheet 47 and to a tester 59through inner wiring (not illustrated) of the electrode plate 48.

A third upper-side anisotropically conductive sheet 25 is arranged onthe front surface of the connector 10 for measurement of electricresistance.

The first upper-side anisotropically conductive sheet 20 in thisembodiment is the so-called uneven distribution type anisotropicallyconductive sheet composed of a plurality of conductive path-formingportions 21 arranged in accordance with a pattern corresponding to thepattern of the relay electrodes 14, 17 of the connector 10 formeasurement of electric resistance and extending in the thickness-wisedirection and insulating portions 22 interposed between these conductivepath-forming portions 21 to mutually insulate these conductivepath-forming portions.

The conductive path-forming portions 21 are each formed by causingconductive particles P exhibiting magnetism to be contained at highdensity in an elastic polymeric substance making up a base material ofthe first upper-side anisotropically conductive sheet 20 in a stateoriented so as to align in the thickness-wise direction thereof.Conductive paths are formed by respective chains of the conductiveparticles P. On the other hand, the insulating portions 22 do notcontain the conductive particles P at all or scarcely contain them.

As examples of the conductive particles P making up the conductivepath-forming portions 21, may be mentioned particles of metalsexhibiting magnetism, such as nickel, iron and cobalt, particles ofalloys thereof and particles containing such a metal; particles obtainedby using these particles as core particles and plating the coreparticles with a metal having good conductivity, such as gold, silver,palladium or rhodium; and particles obtained by using particles of anon-magnetic metal, inorganic particles such as glass beads or polymerparticles as core particles and plating the core particles with aconductive magnetic material such as nickel or cobalt.

Among these, particles obtained by using nickel particles as coreparticles and plating them with a metal having good conductivity, suchas gold or silver are preferably used.

The particle diameter of the conductive particles P is preferably 3 to200 μm, particularly 10 to 100 μm in order that deformation underpressure of the resulting conductive path-forming portions 21 is madeeasy, and sufficient electrical contact is achieved among the conductiveparticles P in the conductive path-forming portions 21.

The water content in the conductive particles P is preferably at most5%, more preferably at most 3%, still more preferably at most 2%,particularly preferably at most 1%. The use of the conductive particlessatisfying such conditions can prevent or inhibit the occurrence ofbubbles in the first upper-side anisotropically conductive sheet 20 uponthe formation thereof.

The proportion of the conductive particles P in the conductivepath-forming portions 21 is preferably 5 to 60%, more preferably 7 to50%, particularly preferably 10 to 40% in terms of volume fraction. Ifthis proportion is lower than 5%, it may be difficult in some cased toform conductive paths sufficiently low in electric resistance value. Ifthe proportion exceeds 60% on the other hand, the resulting conductivepath-forming portions 21 become brittle, so that elasticity required ofthe conductive path-forming portions may not be achieved in some cases.

The insulating elastic polymeric substance making up the base materialof the first upper-side anisotropically conductive sheet 20 ispreferably a polymeric substance having a crosslinked structure. As amaterial for the polymeric substance usable for obtaining the polymericsubstance having the crosslinked structure, may be used variousmaterials. Specific examples thereof include conjugated diene rubberssuch as polybutadiene rubber, natural rubber, polyisoprene rubber,styrene-butadiene copolymer rubber and acrylonitrile-butadiene copolymerrubber and hydrogenated products thereof; block copolymer rubbers suchas styrene-butadiene block copolymer rubber and hydrogenated productsthereof; and silicone rubber, fluorine-containing rubber,silicone-modified fluorine-containing rubber, ethylene-propylenecopolymer rubber, urethane rubber, polyester rubber, chloroprene rubberand epichlorohydrin rubber.

Among these, silicone rubber and silicone-modified fluorine-containingrubber are preferably used in that they are high in molding andprocessing ability and electrical insulating properties.

The second upper-side anisotropically conductive sheet 47 and thirdupper-side anisotropically conductive sheet 25 are the so-calleddispersed type anisotropically conductive sheets that conductiveparticles P are contained in an elastic polymeric substance in a statethey are oriented so as to arrange in rows in a thickness-wise directionthereof to form chains, and the chains by the conductive particles P aredispersed in a plane direction thereof.

As the elastic polymeric substances and conductive particles P making upthese second upper-side anisotropically conductive sheet 47 and thirdupper-side anisotropically conductive sheet 25, may be used the samematerials as the elastic polymeric substance and conductive particles Pmaking up the first upper-side anisotropically conductive sheet 20.

In the lower-side adaptor 50, an other-side circuit board 51 forinspection is provided, and an inspection electrode pair composed of aninspection electrode 52 for current supply and an inspection electrode53 for voltage measurement, which are arranged in a state separated fromeach other, to one other-side electrode 3 to be inspected of the circuitboard 1 to be inspected in accordance with a pattern corresponding to anarrangement pattern of the other-side electrodes 3 to be inspected, isarranged on the front surface (upper surface in FIG. 8) of theother-side circuit board 51 for inspection so as to be located within aregion of an area equivalent to the region occupied by the other-sideelectrode 3 to be inspected. Terminal electrodes 52 a for current supplyand terminal electrodes 53 a for voltage measurement are arrangedaccording to a pattern corresponding to the arrangement pattern ofstandard arrangement electrodes 61 of an electrode plate 60, which willbe described subsequently, on the back surface of the other-side circuitboard 51 for inspection. These terminal electrodes 52 a for currentsupply and terminal electrodes 53 a for voltage measurement arerespectively electrically connected to their corresponding inspectionelectrodes 52 for current supply and inspection electrodes 53 forvoltage measurement.

On the front surface of the other-side circuit board 51 for inspection,are provided common elastic connecting members 56 which each come intocontact with surfaces (upper surfaces in FIG. 8) of both inspectionelectrode 52 for current supply and inspection electrode 53 for voltagemeasurement, which make up the inspection electrode pair. The elasticconnecting members 56 are held by a sheet-like holding member 57provided on the front surface of the other-side circuit board 51 forinspection in a state that their surfaces (upper surfaces in FIG. 8)have projected from the surface of the holding member 57. In theembodiment illustrated in the figure, a plurality of the elasticconnecting members 56 are provided, in a state independently of eachother, corresponding to the respective other-side electrodes 3 to beinspected in the circuit board 1 to be inspected.

The electrode plate 60 is provided on the back surface (lower surface inFIG. 8) of the other-side circuit board 51 for inspection through alower-side anisotropically conductive sheet 62.

The electrode plate 60 and the lower-side anisotropically conductivesheet 62 correspond to the electrode plate 48 and second upper-sideanisotropically conductive sheet 47 in the upper-side adaptor 40,respectively. The electrode plate 60 has, on the surface thereof (uppersurface in FIG. 8), the standard arrangement electrode 61 arranged onstandard lattice points having a pitch of, for example, 2.54 mm, 1.8 mmor 1.27 mm. The standard arrangement electrodes 61 are respectivelyelectrically connected to the terminal electrodes 52 a for currentsupply or the terminal electrodes 53 a for voltage measurement of theother-side circuit board 51 for inspection through the lower-sideanisotropically conductive sheet 62 and to the tester 59 through innerwiring (not illustrated) of the electrode plate 60.

The elastic connecting members 56 are preferably formed by, for example,an anisotropically conductive elastomer that exhibits high conductivityin its thickness-wise direction. In such an anisotropically conductiveelastomer, conductive particles are filled into, for example, aninsulating elastic polymeric substance in a state oriented so as toalign in the thickness-wise direction (vertical direction in thedrawings), thereby exhibiting high conductivity in the thickness-wisedirection. In particular, a pressure-sensitive anisotropicallyconductive elastomer that conductive paths extending in thethickness-wise direction are formed when it is pressurized andcompressed in the thickness-wise direction is preferred.

Such elastic connecting members 56 can be formed in accordance with anyproper process, for example, a process described in Japanese PatentApplication Laid-Open No. 2000-74965.

Each of the elastic connecting members 56 preferably has higherconductivity in its thickness-wise direction than that in a planedirection perpendicular to the thickness-wise direction. Specifically,the elastic connecting member 56 preferably has electrical propertiesthat a ratio of the electric resistance value in the thickness-wisedirection to the electric resistance value in the plane direction is 1or lower, particularly 0.5 or lower.

If the ratio exceeds 1, a current flowing between the inspectionelectrode 52 for current supply and the inspection electrode 53 forvoltage measurement through the elastic connecting member 56 becomeshigh, so that it may be difficult in some cases to measure electricresistance with high precision.

From such a point of view, when the elastic connecting members 56 areformed by causing conductive particles to be contained in an insulatingelastic polymeric substance, the filling rate of the conductiveparticles is preferably 5 to 50% by volume.

A clearance between the inspection electrode 52 for current supply andthe inspection electrode 53 for voltage measurement in the other-sidecircuit board 51 for inspection is preferably at least 10 μm. If thisclearance is shorter than 10 μm, a current flowing between theinspection electrode 52 for current supply and the inspection electrode53 for voltage measurement through the elastic connecting member 56becomes high, so that it may be difficult in some cases to measureelectric resistance with high precision.

On the other hand, the upper limit of the clearance is determined by thesize of the respective inspection electrodes and the size and pitch oftheir corresponding other-side electrodes 3 to be inspected, and isgenerally at most 500 μm. If this clearance is too long, it may bedifficult in some cases to suitably arrange both inspection electrodesto one of the other-side electrodes 3 to be inspected.

In the above-described electric resistance-measuring apparatus forcircuit boards, an electric resistance between any one-side electrode 2to be inspected and its corresponding other-side electrode 3 to beinspected in the circuit board 1 to be inspected is measured in thefollowing manner.

The circuit board 1 to be inspected is arranged at a necessary positionbetween the upper-side adaptor 40 and the lower-side adaptor 50, and inthis state, the upper-side adaptor 40 is lowered, and the lower-sideadaptor 50 is lifted, thereby bringing the third upper-sideanisotropically conductive sheet 25 into contact under pressure with onesurface of the circuit board 1 to be inspected and at the same time,bringing the elastic connecting members 56 of the lower-side adaptor 50into contact under pressure with the other surface of the circuit board1 to be inspected. This state is a measurable state.

Specifically described with reference to FIG. 9, in this measurablestate, the core electrodes 13 and ring-like electrodes 15 in theconnector 10 for measurement of electric resistance are electricallyconnected at the same time to their corresponding one-side electrodes 2to be inspected of the circuit board 1 to be inspected through theconductive paths formed in the third upper-side anisotropicallyconductive sheet 25. The core electrodes 13 and ring-like electrodes 15are in a state electrically independent of each other.

On the other hand, the inspection electrode pairs each composed of theinspection electrode 52 for current supply and the inspection electrode53 for voltage measurement are electrically connected to theircorresponding other-side electrodes 3 to be inspected of the circuitboard 1 to be inspected through the elastic connecting members 56.

In such a state, one of a plurality of the one-side electrodes 2 to beinspected in the circuit board 1 to be inspected is designated, and oneof the core electrode 13 and ring-like electrode 15 electricallyconnected to this designated electrode 2 to be inspected is used as anelectrode for current supply, and the other is used as an electrode forvoltage measurement, whereby a current is supplied between the coreelectrode 13 or ring-like electrode 15 used as the electrode for currentsupply and the inspection electrode 52 for current supply of theinspection electrode pair electrically connected to the other-sideelectrode 3 to be inspected corresponding to the designated one-sideelectrode 2 to be inspected, and at the same time, voltage between thecore electrode 13 or ring-like electrode 15 used as the electrode forvoltage measurement and the inspection electrode 53 for voltagemeasurement of the inspection electrode pair electrically connected tothe other-side electrode 3 to be inspected corresponding to thedesignated one-side electrode 2 to be inspected is measured, wherebymeasurement of an electric resistance between the designated one-sideelectrode 2 to be inspected and its corresponding other-side electrode 3to be inspected can be performed.

According to the electric resistance-measuring apparatus for circuitboards of the above-described construction, the connector 10 formeasurement of electric resistance of the construction shown in FIG. 1is provided, so that at least a part of the ring-like electrode 15 islocated on the one-side electrode 2 to be inspected in the circuit board1 to be inspected so far as alignment is conducted in such a manner thatat least a part of the core electrode 13 in the connector 10 formeasurement of electric resistance is located on the one-side electrode2 to be inspected, whereby electrical connection of both core electrodes13 and ring-like electrodes 15 to the one-side electrodes 2 to beinspected can be surely achieved even when the circuit board 1 to beinspected is large in area and has a great number of small-sizedone-side electrodes 2 to be inspected. In addition, since the coreelectrodes 13 and ring-like electrodes 15 are electrically insulatedfrom each other, an electric resistance as to the circuit board 1 to beinspected can be measured with high precision by using one of the coreelectrode 13 and ring-like electrode 15 electrically connected to theone-side electrode 2 to be inspected as an electrode for current supplyand the other as an electrode for voltage measurement.

The present invention is not limited to the above-described embodiments,and such various changes or modifications as described below may beadded thereto.

For example, the third upper-side anisotropically conductive sheet 25 isnot essential, and the electric resistance-measuring apparatus forcircuit boards may be so constructed that the core electrodes 13 andring-like electrodes 15 in the connector 10 for measurement of electricresistance come into direct contact with the one-side electrodes 2 to beinspected.

As the other-side circuit board 51 for inspection of the lower-sideadapter 50, those of various types may be used so far as a state thatthe inspection electrode 52 for current supply and inspection electrode53 for voltage measurement making up the inspection electrode pair havebeen electrically connected to one of the other-side electrodes 3 to beinspected can be achieved.

As the elastic connecting members 56, may also be used ananisotropically conductive elastomer having conductive path-formingportions, which extend, independently of each other, in thethickness-wise direction at positions corresponding to the inspectionelectrodes 52 for current supply and the inspection electrodes 53 forvoltage measurement, and insulating portions for electrically insulatingthe conductive path-forming portions from one another.

Inspection electrodes, on the tips of which a conductive elastomer isprovided, and further probe pins, if permitted, may also be used asinspection electrodes.

When the circuit board to be inspected, which is subjected to electricresistance measurement, has protruding one-side electrodes to beinspected, that of the construction shown in FIG. 7 is preferably usedas the connector 10 for measurement of electric resistance.

According to the electric resistance-measuring apparatus having such aconnector 10 for measurement of electric resistance, as illustrated inFIG. 10, the conductors 12 of the connector 10 for measurement ofelectric resistance are moved in the thickness-wise direction accordingto the projected height of protruding one-side electrodes 2 to beinspected when the third upper-side anisotropically conductive sheet 25are brought into contact under pressure with the one-side electrodes 2to be inspected, so that the irregularity-absorbing properties of thesecond upper-side anisotropically conductive sheet 20 and thirdupper-side anisotropically conductive sheet 25 can be effectivelyutilized. Accordingly, high reliability on connection is achieved evento a circuit board 1 to be inspected that has protruding one-sideelectrodes 2 to be inspected projected from the one surface, a scatterof projected height of said protruding one-side electrodes 2 to beinspected being great. As a result, necessary measurement of electricresistance can be surely performed with high precision.

The present invention will hereinafter be described specifically by thefollowing Examples. However, the present invention is not limitedthereto.

In the following Examples, a single-sided printed circuit board of thefollowing specification was used as a circuit board to be inspected.

A single-sided printed circuit board having dimensions of 4 cm long by15 cm wide, in which 6 electrode groups in total each composed of 64electrodes to be inspected having a diameter of 300 μm and arranged at apitch of 0.5 mm are formed on one surface thereof (the total number ofelectrodes to be inspected: 384), and every 2 electrodes among the 64electrodes to be inspected in each electrode group are electricallyconnected to each other through inner wiring to form a circuit (thenumber of circuits in each electrode group: 32; the total number ofcircuits: 192).

EXAMPLE 1

A base plate material obtained by integrally forming copper foils havinga thickness of 12 μm on both surfaces of an insulating base platecomposed of a glass fiber-reinforced epoxy resin and having dimensionsof 5 cm long by 18 cm wide and a thickness of 100 μm was provided, and aplurality of through-holes for short circuit parts having a diameter of120 μm were formed correspondingly to short circuit parts in theintended connector for measurement of electric resistance in this baseplate material by means of an NC drilling machine. Positions, at whichthese through-holes for short circuit parts are formed, were positions250 μm away from respective central positions of core electrodes in theintended connector for measurement of electric resistance.

The base plate material, in which the through-holes for short circuitparts had been formed, was then subjected to a plating treatment withcopper under conditions of 25° C. and 45 minutes, thereby forming shortcircuit parts within the through-holes for short circuit parts.Photolithography and an etching treatment were then conducted, wherebycircular electrode layers for formation of ring-like electrodes, whichhad a diameter of 150 μm, and wiring parts for linking the circularelectrode layers with the short circuit parts, respectively, were formedon the front surface of the insulating base plate.

Through-holes each having an inner diameter of 100 μm and extendingthrough the insulating base plate and circular electrode layer andhaving an inner diameter of 100 μm were then formed in this base platematerial by means of the NC drilling machine, thereby forming ring-likeelectrodes having an outer diameter of 150 μm and an inner diameter of100 μm. Thereafter, liquid silicone rubber was filled into each of thethrough-holes and cured, thereby forming columnar filler members in therespective through-holes.

The respective filler members were then subjected to laser beammachining, from the back surface side, thereby forming truncatedcone-like through-holes for formation of conductors. The through-holesfor formation of the conductors had an opening diameter of 80 μm on theside of a front surface and an opening diameter of 100 μm on the side ofa back surface. The interiors of the through-holes for formation of theconductors in the respective filler members were then subjected to aplating treatment with copper, thereby forming truncated cone-likeconductors composed of copper, the front surface-side ends of which wereprovided as core electrodes having a diameter of 70 μm, and the backsurface-side ends of which were provided as relay electrodes having adiameter of 100 μm, in the through-holes for formation of theconductors.

The copper foil formed on the back surface of the insulating base platewas then subjected to photolithography and an etching treatment, therebyforming relay electrodes having a diameter of 100 μm, which wereelectrically connected to their corresponding ring-like electrodesthrough the respective short circuit parts and wiring parts, to producea connector for measurement of electric resistance.

Incidentally, in the above-described process, a resist layer was formedon both surfaces of the insulating base plate except for the time forsurface processing to protect it.

The connector for measurement of electric resistance produced in such amanner was used to produce an electric resistance-measuring apparatushaving only an upper-side adaptor shown in FIG. 8.

Comparative Example 1

An electric resistance-measuring apparatus having a circuit board forinspection, on the front surface of which electrodes for current supplyand electrodes for voltage measurement were formed corresponding toelectrodes to be inspected, a connecting member composed of a conductiveelastomer provided on a front surface of the circuit board forinspection, and a holding member was produced in accordance with theconstruction described in Japanese Patent Application Laid-Open No.2000-74965.

In the circuit board for inspection, the electrodes for current supplyand electrodes for voltage measurement each had dimensions of 50 μm by100 μm, a clearance between the electrode for current supply and theelectrode for voltage measurement was 150 μm, the thickness of theconnecting member was 0.4 mm, silicone rubber was used as an elasticpolymeric substance for forming the connecting member, and nickelparticles plated with gold, which had an average particle diameter of 40μm, were used as conductive particles.

[Evaluation]

A total of 100 circuit boards to be inspected of the above-describedspecification were provided, and an electric resistance of each circuitin these circuit boards to be inspected was measured by means of theelectric resistance-measuring apparatus according to Example 1 andComparative Example 1 to make a judgment of bad connection when themeasured value of the electric resistance in the circuit was 1 Ω orhigher, thereby counting the number thereof.

As a result, the number of circuits exhibiting the electric resistancevalue of 1 Ω or higher was 0 among 19,200 circuits (192 circuits×100) inthe electric resistance-measuring apparatus according to Example 1, butwas 510 among 19,200 circuits in the electric resistance-measuringapparatus according to Comparative Example 1.

Effects of the Invention

According to the present invention, as described above, there can beprovided connectors for measurement of electric resistance, and electricresistance-measuring apparatus for circuit boards and methods ofmeasurement of electric resistance, by which necessary electricalconnection to a circuit board to be inspected, which is subjected toelectric resistance measurement, can be surely achieved even when thecircuit board to be inspected is large in area and has a great number ofsmall-sized electrodes to be inspected, and expected measurement ofelectric resistance can be surely performed with high precision.

1. A connector for measurement of electric resistance, comprising: aninsulating base plate, a plurality of connecting electrode pairsprovided on a front surface of the insulating base plate and arranged inaccordance with a pattern corresponding to a pattern of a plurality ofelectrodes on a circuit board to be inspected using an electricresistance measurement, wherein each connecting electrode paircomprises: a core electrode having an end part extending to the frontsurface of the base plate and an other end part extending to a backsurface of the base plate, the core electrode being supported by theinsulating plate such that the core electrode can move in athickness-wise direction with respect to the insulating plate; and aring-like electrode arranged on the front surface so as to surround thecore electrode in a state electrically insulated from the coreelectrode, and a plurality of relay electrodes provided on a backsurface of the insulating base plate, each relay electrode beingelectrically connected to either one of the core electrode, or ring-likeelectrode of a respective connecting electrode pair.
 2. A connector formeasurement of electric resistance according to claim 1, which isarranged on one side of a circuit board to be inspected, wherein thecore electrodes and ring-like electrodes of the connecting electrodepairs of the connector are electrically connected at the same time torespective electrodes on the circuit board to be inspected, therebyrealizing a measurable state, and in the measurable state, one of thecore electrode and ring-like electrode electrically connected to onedesignated electrode to be inspected is used as an electrode for currentsupply and the other is used as an electrode for voltage measurement,thereby performing measurement of electric resistance related to thedesignated one electrode to be inspected.
 3. The connector formeasurement electric resistance according to claim 2, wherein in themeasurable state, the connecting electrode pairs are electricallyconnected with their corresponding relay electrodes through ananisotropically conductive sheet.
 4. A method of measurement of electricresistance for circuit boards, which comprises arranging the connectorfor measurement of electric resistance according to claim 1 on one sideof a circuit board to be inspected, which is subjected to electricresistance measurement, electrically connecting the core electrodes andring-like electrodes of the connecting electrode pairs of the connectorfor measurement of electric resistance at the same time to respectiveone-side electrodes to be inspected of the circuit board to beinspected, thereby realizing a measurable state, and in this measurablestate, using one of the core electrode and ring-like electrodeelectrically connected to one designated one-side electrode to beinspected as an electrode for current supply and the other as anelectrode for voltage measurement, thereby performing measurement ofelectric resistance related to the designated a one-side electrode to beinspected.
 5. The connector for measurement of electric resistanceaccording to claim 1, wherein the core electrode comprises a taperedcross-sectional shape that increases in width as the core electrodeextends toward the back surface of the base plate.
 6. The connector formeasurement of electric resistance according to claim 1, wherein adiameter of the core electrode is 30–80% of the diameter of theelectrode on the circuit board to be inspected.
 7. The connector formeasurement of electric resistance according to claim 6, wherein aninner diameter of ring-like electrode is 50–100% of the diameter of theelectrodes to be inspected.
 8. An electric resistance-measuringapparatus for circuit boards, comprising: a first connector formeasuring a first side of a circuit board, comprising: a firstinsulating base plate, a plurality of first connecting electrode pairsprovided on a front surface of the first insulating base plate andarranged in accordance with a pattern corresponding to a pattern of aplurality of electrodes on the first side of the a circuit board to beinspected using an electric resistance measurement, wherein each firstconnecting electrode pair comprises: a first core electrode having anend part extending to the front surface of the first base plate and another end part extending to a back surface of the first base plate, thefirst core electrode being supported by the insulating plate such thatthe first core electrode can move in a thickness-wise direction withrespect to the first insulating plate, and a first ring-like electrodearranged on the front surface so as to surround the first core electrodein a state electrically insulated from the first core electrode, and aplurality of first relay electrodes provided on a back surface of theinsulating base plate, each relay electrode being electrically connectedto either one of the first core electrode, or first ring-like electrodeof a respective first connecting electrode pair; and a second connectorfor measuring a second side of a circuit board, comprising: a secondinsulating base plate, a plurality of second connecting electrode pairsprovided on a front surface of the second insulating base plate andarranged in accordance with a pattern corresponding to a pattern of aplurality of electrodes on the second side of the a circuit board to beinspected using an electric resistance measurement, wherein each secondconnecting electrode pair comprises: a second core electrode having anend part extending to the front surface of the second base plate and another end part extending to a back surface of the second base plate, thesecond core electrode being supported by the insulating plate such thatthe second core electrode can move in a thickness-wise direction withrespect to the second insulating plate, and a second ring-like electrodearranged on the front surface so as to surround the second soreelectrode in a state electrically insulated from the second coreelectrode, and a plurality of second relay electrodes provided on a backsurface of the insulating base plate, each relay electrode beingelectrically connected to either one of the second core electrode, orsecond ring-like electrode of a respective second connecting electrodepair.
 9. An electric resistance-measuring apparatus for circuit boardsaccording to claim 8, wherein the core electrodes and ring-likeelectrodes of the connecting electrode pairs of the first or secondconnector are electrically connected at the same time to respectiveelectrodes in the circuit board to be inspected, thereby realizing ameasurable state, and in the measurable state, one of the core electrodeand ring-like electrode electrically connected to one designatedelectrode to be inspected is used as an electrode for current supply andthe other is used as an electrode for voltage measurement, therebyperforming measurement of electric resistance related to the designatedone electrode to be inspected.
 10. The connector for measurement ofelectric resistance according to claim 8, wherein, in the measurablestate, the connecting electrode pairs of the first or second boards areelectrically connected with their corresponding relay electrodes throughan anisotropically conductive sheet.
 11. The connector for measurementof electric resistance according to claim 8, wherein at least one of thefirst or second core electrodes comprise a tapered cross-sectional shapethat increases in width as the core electrode extends toward the backsurface of the base plate.
 12. The connector for measurement of electricresistance according to claim 8, wherein a diameter of at least one ofthe first or second core electrodes is 30–80% of the diameter of theelectrode on the circuit board to be inspected.
 13. The connector formeasurement of electric resistance according to claim 12, wherein aninner diameter of at least one of the first or second ring-likeelectrode is 50–100% of the diameter of the electrodes to be inspected.